1. Field of the Invention
The present invention relates in general to scalable image processing, and more specifically to a localized content adaptive system and method for selecting or programming re-sampling low-pass filters for low power multiple rate scalable image processing.
2. Description of the Related Art
The Advanced Video Coding (AVC) standard, Part 10 of MPEG4 (Motion Picture Experts Group), otherwise known as H.264, includes advanced compression techniques that were developed to enable transmission of video signals at a wide range of bit rates or to enable improved video quality at a given transmission rate. The newer H.264 standard outperforms video compression techniques of prior standards in order to support higher quality video at given bit rates and to enable internet-based video and wireless applications and the like. The standard defines the syntax of the encoded video bit stream along with a method of decoding the bit stream. Scalable Video Coding (SVC) is an extension of the H.264 which addresses coding schemes for reliably delivery of video to diverse clients over heterogeneous networks using available system resources, particularly in scenarios where the downstream client capabilities, system resources, and network conditions are not known in advance, or dynamically changing from time to time.
SVC achieves scalability by using base and enhanced layers concept, where an enhanced layer, or upper layer, is scalable from a lower layer, e.g., a base layer. Whereas H.264 has relatively limited scalability, SVC provides multiple levels of scalability including temporal scalability, spatial scalability, complexity scalability and quality scalability. The base layer should be the simplest form in quality, spatial resolution and temporal resolution. Temporal scalability generally refers to the number of frames per second (fps) of the video stream, such as 7.5 fps, 15 fps, 30 fps, etc. Spatial scalability refers to the resolution of each frame, such as common interface format (CIF) with 352 by 288 pixels per frame, or quarter CIF (QCIF) with 176 by 144 pixels per frame, although other spatial resolutions are contemplated, such as 4CIF, QVGA, VGA, SVGA, D1, HDTV, etc. Complexity scalability generally refers to the various computational capabilities and processing power of the devices processing the video information. Quality scalability refers to various bitrates, such as quantization levels, and is generally measured with a peak signal-to-noise (PSNR) metric versus bitrate defining the relative quality of a reconstructed image compared with an original image. The present disclosure primarily concerns an adaptive filtering system used during up and down sampling for spatial scalability.
Up and down sampling of an image signal is a common function performed in image communication systems including video systems. The up and down sampling functions incorporate a low pass filter function, which tends to blur an image or video frame. It is desired to preserve the sharpness of each image or video frame. In the current development process for SVC, up and down sampling of a video frame or a macroblock is used for inter-layer texture predictions. Two fixed length FIR filters are used in the encoder and decoder of the Joint Scalable Verification Model (JSVM). Fixed length filters, however, may result in suboptimal performance in anti-aliasing and anti-imaging for down and up sampling due to the variations of characteristics in frequency, spatial and time domain of such two-dimensional signals. Longer filter taps results in additional power consumption and memory requirements.
It is desired to provide an adaptive filter for balancing the tradeoff between visual quality, power and memory consumption for image processing.